Oil content in semi-refined paraffin wax is the percentage of residual mineral oil left after refining, tested by methods such as ASTM D721, and it directly affects hardness, melting point, flexibility and pour behaviour. Semi-refined grades carry more residual oil than more heavily processed grades, which buyers in candles, cosmetics and industrial applications specify and verify against a stated test method rather than a descriptive label.
What is oil content in semi-refined paraffin wax? Oil content is the residual mineral oil left in a paraffin wax after the refining process, measured as a percentage of the wax's weight. Semi-refined paraffin wax typically carries a higher oil content than more heavily processed grades, and that oil content is the single number that tells a buyer how the wax will behave — its hardness, its melting point, and how it blends. This guide, What Is Oil Content In Semi-Refined Paraffin Wax, walks through what the figure means, how it is tested, and what to check before you place an order.
- Oil content is measured by extracting oil from a wax sample, most commonly with the ASTM D721 method.
- ASTM D721 applies to petroleum waxes with a congealing point of 30°C (86°F) or higher.
- Higher oil content generally means a softer, more flexible wax with a lower melting point.
- Regulatory limits exist for specific end uses — for example, 21 CFR 175.250 sets an oil-content ceiling for a defined food-contact application.
- China's GB/T 254-2022 is the current national standard specifically covering semi-refined paraffin wax.
Who this guide is for
This article is written for three buyers who ask the same question in different words. Candle makers and wax distributors want to know how oil content changes pour behaviour and scent-throw in container and economy candle lines. Cosmetics and personal-care formulators want to know how oil content affects texture in balms and creams. Procurement teams sourcing at volume want a defensible way to specify and verify the grade they are paying for. Each section below speaks to one of these questions directly.
What is oil content, technically?
Paraffin wax is a byproduct of lubricant oil production, and a certain amount of oil is inherently difficult to remove completely during refining, according to Energy & Fuels, ACS Publications (2014). The standard laboratory method, ASTM D721, extracts that residual oil with methyl ethyl ketone at −32°C — a process the same study describes as slow and only moderately precise. That is worth knowing before treating any single oil-content figure as an exact science: it is a controlled, repeatable test, not a perfect one.
Chemically, petroleum waxes are mixtures of n-paraffins, branched-chain paraffins and cycloparaffins spanning roughly C18 to C70, according to IntechOpen. The oil trapped within that mixture is what separates one grade from another on the refining spectrum.
Why oil content matters to a buyer
According to ASTM International (2025), oil content can significantly affect a wax's strength, hardness, flexibility, scuff resistance, coefficient of friction, coefficient of expansion, melting point and oil staining. That is a long list, and it is the reason oil content is usually the first spec a buyer checks, ahead of colour or odour. A wax bought for the wrong oil-content range will underperform in the application it was bought for, regardless of price.
Semi-refined vs. more heavily processed grades
Refining reduces oil content step by step. A semi-refined wax sits earlier on that spectrum than a more heavily processed grade, and it typically carries more residual oil as a result. Buyers researching what is oil content in semi-refined paraffin wax are usually trying to work out whether that higher oil content is a limitation or simply a property to design around — for most industrial and utility applications, it is the latter.
How oil content is tested and standardised
| Standard | What it measures | Why a buyer checks it |
|---|---|---|
| ASTM D721-25 | Oil content of petroleum waxes with a congealing point of 30°C or higher | The primary US laboratory reference method for verifying a supplier's oil-content claim |
| ISO 2908:1974 (withdrawn) | Oil-content test procedure for petroleum waxes containing not more than 15% oil, congealing point 30°C or higher | Historical reference point for oil-content testing outside the US; useful context when comparing older specification sheets |
| 21 CFR 175.250 | Sets an oil-content ceiling of 2.5% (by ASTM D721-56T) for a specific regulated food-contact use | Shows how tightly a regulator can bound oil content for one defined application — a useful benchmark, not a general limit |
| GB/T 254-2022 | China's current national standard for semi-refined paraffin wax | Relevant when specifying or comparing wax sourced against Chinese national grades |
Application-by-application guidance
Candle making: container, economy and mourning candles
Waxes from BHD Group's range are used to make pillar candles, an application with published client evidence behind it. Buyers working in economy and utility candles, container candles, and grave, church or mourning candles size their oil-content requirement to the pour and burn behaviour they need — a softer, higher-oil wax pours differently than a harder one, and getting that match right up front avoids reformulating mid-run. Slack-wax blending is a related route some buyers use to fine-tune oil content and hardness for a specific candle line.
Cosmetics and personal care: balms and creams
Waxes are also used to make cosmetic creams and balms, a confirmed application. Formulators in this space check oil content because it drives texture — spreadability, firmness and melt-on-skin feel all shift with it. Anyone specifying wax for balm or cream production should ask a supplier for the oil-content figure alongside the congealing point, not one without the other.
Procurement: specifying and verifying the number
For a procurement lead, the oil-content figure is only useful if it is verifiable. Ask which test method a supplier used (ASTM D721 remains the reference point most buyers request), and ask for the figure as a specific percentage on the certificate of analysis rather than a descriptive term like "low oil" or "high oil."
What to check before you order
- Request the oil-content percentage in writing, not a qualitative description.
- Confirm which test method produced the figure — ASTM D721 is the most widely referenced.
- Ask for the congealing point alongside oil content — the two properties are read together.
- If the wax is for a food-contact use, check the regulatory ceiling that applies to that specific use.
- For candle applications, match oil content to the pour type — container, economy, or mourning candle lines each tolerate a different range.
- For cosmetics use, request a sample batch and test texture before committing to volume.
- Ask whether the certificate of analysis is batch-specific or a generic product sheet.
- Confirm origin and processing history — oil content is a downstream result of how the wax was refined.
Working with BHD Group
BHD Group operates as one accountable house across two divisions, BHD Chemical and BHD Sourcing. Paraffin wax sits inside the wax range BHD Chemical leads with, alongside Petroleum Jelly and Slack Wax, and the same origin-integrity approach applies across the range: buyers get a specific figure against a named test method, not a vague assurance. If you are evaluating semi-refined paraffin wax for a candle, cosmetics or industrial application and want to talk through oil-content specification against your own process, BHD Group is the house to bring that conversation to.
Sources
- ASTM International (2025) — Standard Test Method for Oil Content of Petroleum Waxes (ASTM D721-25) — https://store.astm.org/d0721-25.html
- ISO (1974) — ISO 2908:1974, Petroleum waxes — Determination of oil content — https://www.iso.org/standard/7947.html
- U.S. Electronic Code of Federal Regulations — 21 CFR 175.250, Paraffin (synthetic) — https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-175/subpart-C/section-175.250
- Energy & Fuels, ACS Publications (2014) — Characterization of the Composition of Paraffin Waxes on Industrial Applications — https://doi.org/10.1021/ef4021813
- IntechOpen — Introductory Chapter: Petroleum Paraffins — https://api.intechopen.com/chapter/pdf-download/67759.pdf
- chinesestandard.net (2022) — GB/T 254-2022, Semi-refined paraffin wax — https://www.chinesestandard.net/PDF/English.aspx/GBT254-2022
Frequently asked questions
What is what is oil content in semi-refined paraffin wax?
It is the percentage of residual mineral oil remaining in a paraffin wax after refining. Semi-refined grades sit earlier on the refining spectrum than more heavily processed grades and typically carry more residual oil, which is measured against standards such as ASTM D721.
How does what is oil content in semi-refined paraffin wax work?
Oil is extracted from a wax sample in a laboratory test — ASTM D721 uses methyl ethyl ketone at −32°C — and the extracted amount is expressed as a percentage of the wax's weight. That figure is then read alongside the congealing point to describe how the wax will behave in use.
What are the benefits of what is oil content in semi-refined paraffin wax?
Knowing the oil-content figure lets a buyer predict hardness, flexibility, melting point and pour behaviour before committing to volume, and it gives procurement a verifiable spec to check against a certificate of analysis rather than relying on a supplier's descriptive claim.
Why buyers work with BHD Group
Two divisions operate under a single accountable house. There is no handoff between a trading desk and a sourcing desk that leaves a buyer chasing an answer — one team owns the order from enquiry to delivery.
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